The present invention pertains to a respirator for supplying a patient with breathing gas and to a process for controlling the respirator.
A respirator, with which both mechanical and manual respiration can be performed, has been known from U.S. Pat. No. 5,875,777. To adapt the mechanical respiration to the breathing pattern of manual respiration as closely as possible, certain parameters of respiration, such as the breathing gas flow, the airway pressure and the duration of inspiration and expiration are measured and stored. The manual respiration is reproduced during the mechanical respiration on the basis of these data. To eliminate stochastic fluctuations, the measured values obtained during the manual respiration are evaluated over a larger number of breathing cycles in order to then form mean values.
Respirators used in anesthesia or intensive care offer a large number of forms of mechanical respiration, besides the purely manual respiration, in order to optimally supply the patient with breathing air. These forms of respiration are controlled either purely by the pressure or purely by the volume, and numerous mixed forms between volume-controlled and pressure-controlled respiration are used as well. The problem faced by the user is not only to carry out the changeover from manual respiration to mechanical respiration possibly without a transition, but also to carry out the changeover between the mechanical forms of respirations such that the time of the changeover will not be perceived by the patient. To achieve this, setting parameters that are needed for the new form of respiration but are inactive during the current form of respiration must be set as adequately as possible.
The primary object of the present invention is to improve a respirator such that the respiration is not compromised during the changeover from one form of respiration to another form of respiration and to provide a process for controlling the respirator.
According to the invention, a respirator is provided with a volume-shifting device, which is designed to carry out preselected forms of respiration. A gas line system is connected to the volume-shifting device for supplying a patient with breathing gas. Measuring devices are provided for at least the airway pressure and the breathing gas flow, wherein at least a plateau pressure Pplat and a said inspiratory volume VT are determined as measured values. A control unit is provided which contains an input unit for setting at least a first form of respiration and a second form of respiration as well as for entering at least first setting parameters belonging to the first form of respiration. The control unit generates control signals for at least the volume-shifting device in order to carry out the first form of respiration with the first setting parameters. The control unit is designed such that at the time of a changeover to the second form of respiration, the corresponding setting parameters are selected at least partially from among the measured values determined during the first form of respiration and they are taken over as second setting parameters for the second form of respiration.
According to another aspect of the invention, a respirator is provided containing a volume-shifting device. The respirator is designed to carry out preselected forms of respiration. A gas line system is connected to the volume-shifting device for supplying a patient with breathing gas. A manual respiration device is connected to the gas line system. Measuring devices for at least the airway pressure, the breathing gas flow and the breathing time are provided. At least a plateau pressure Pplat, an inspiratory volume VT, an inspiration time Ti and a expiration time Te are determined as measured values. A control unit is provided, which contains an input unit for setting a manual form of respiration and a mechanical form of respiration with corresponding setting parameters. The control unit generates control signals for the volume-shifting device during the mechanical form of respiration in order to carry out the respiration with the setting parameters. The measured values determined during the manual form of respiration for the inspiration time Ti, expiration time Te and the plateau pressure Pplat are taken over as setting parameters.
According to another aspect of the invention, a process for controlling a respirator, is provided wherein the respirator has a volume-shifting device for carrying out preselected forms of respiration. A gas line system is connected to the volume-shifting device for supplying a patient with breathing gas. Measuring devices are provided for at least the airway pressure Paw and the breathing gas flow, wherein at least a said plateau pressure Pplat and a said inspiratory volume VT are determined as measured values. A first form of respiration is carried out with first setting parameters. The measured values, Pplat or VT, which are not first setting parameters, are determined during the first form of respiration. At the time of a changeover to a second form of respiration, the corresponding setting parameters are selected at least partially from among the measured values determined during the first form of respiration and are taken over as second setting parameters for the second form of respiration.
The advantage of the present invention is essentially that the setting parameters for mechanical forms of respiration that are not active during a form of respiration being currently performed but are needed for carrying out another form of respiration are determined as measured values during the form of respiration currently being set and these are taken over as setting parameters at the time of the changeover to a new form of respiration.
To carry out a first form of respiration in the respirator described in the present invention, first setting parameters are entered via the input unit into the control device. The volume-shifting device receives corresponding control signals from the control unit in order to carry out the first form of respiration. Discrete measured values, e.g., the plateau pressure Pplat, the inspiratory volume VT, or the mean inspiratory flow Vinsp, determined as a volume per unit of time, are determined with the measuring devices present in the breathing circuit for the breathing gas flow and the airway pressure.
At the time of the changeover to a second form of respiration, which has second setting parameters, the second setting parameters are taken over partially or even completely from the discrete measured values determined during the first form of respiration and, if possible, from the first setting parameters. Before the respiration with the second setting parameters is carried out, these are first displayed once again to the user, so that he can check them and take them over by actuating an acknowledge button.
The volume-shifting device needed to carry out mechanical respiration may have various designs. Usual embodiments are a bellows pump, a blower in the form of a radial flow compressor, or even a controllable metering valve, which is arranged downstream of a pressurized gas tank filled with breathing gas.
It is expedient to set certain setting parameters as fixed parameters on an input unit and to adapt other setting parameters in a need-adapted manner. Fixed setting parameters for different forms of respiration are, e.g., the end-expiratory pressure (PPEEP), the inspiration time Ti and the expiration time Te. If a volume-controlled respiration is carried out as the first form of respiration, the first setting parameters also contain the inspiratory volume VT, besides the values set as fixed values for PPEEP, Ti and Te. At the time of the transition of a second form of respiration, a pressure-controlled respiration, a maximum airway pressure Pinsp must be preset. This maximum airway pressure is determined during the first form of respiration as a plateau pressure Pplat and is taken over as a setting parameter for Pinsp during the second form of respiration. If a pressure-controlled respiration is carried out first in the reverse case, the maximum airway pressure Pinsp is preset as a setting parameter and the inspiratory volume VT is determined as a measured value during the pressure-controlled respiration. The inspiratory volume VT measured previously is taken over as a setting parameter during the volume-controlled respiration carried out subsequently. In addition to the inspiratory volume VT, the mean inspiratory flow Vinsp, determined as a volume per unit of time, may be determined as an additional measured variable during the pressure-controlled respiration.
The process for controlling a respirator described in the present invention consists of determining measured values for the plateau pressure Pplat or the inspiratory volume VT by means of the measuring devices for the airway pressure and the inspiratory flow during a first form of respiration with first setting parameters and of selecting the corresponding second setting parameters at least partially from among the measured values determined during the first form of respiration at the time of changeover to a second form of respiration and of taking them over as second setting parameters for the second form of respiration.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.